DE 41 03 588 C1 and EP 0 531 993 B1 describe an X-ray computer tomograph having a rotatable measuring system in which an X-ray source and a detector are arranged in an opposite arrangement so as to be able to rotate about a common axis. To produce sectional images, a patient accommodated on a couch is irradiated in spiral fashion. The X-ray radiation emerging from the patient is detected using the detector and is then converted into a sectional image by, means of computer using a suitable algorithm. To produce a topographical overview shot or a silhouette, a further algorithm is provided which can be used to produce the desired silhouette from the image data for a prescribed angular position which are recorded together with the respective angular position of the measuring system.
The image data used to produce the silhouette are not captured at the same time rather in steps. In this context, the patient is moved in the z-direction. Known X-ray computer tomographs are not suitable for producing angiographical images. A contrast agent administered to the patient changes its distribution in the body over time. When the image data are recorded in steps or at different times, the contrast agent cannot be shown or at least cannot be shown exactly.
EP 0 919 185 A1 discloses an X-ray computer tomograph which is combined with a C-arc X-ray apparatus in order to produce angiographical images. The known X-ray computer tomograph requires a high level of production outlay. To change between the X-ray diagnosis methods, the patient needs to be moved from one X-ray apparatus to the other. This requires the provision of a specially designed couch which can be moved a long way in the z-direction. Apart from this, moving patients with life-threatening injuries, in particular, results in a time delay which is a drawback from the point of view an emergency doctor.
DE 197 21 535 A1 describes an X-ray computer tomograph in which a silhouette is produced by locking the measuring system in a prescribed angular position and then moving the patient in the z-direction. The image data recorded in succession for various z-positions are then processed further using a computer to produce the silhouette. In this context, the measuring system may also comprise a multirow detector or a matrix detector. Using such a matrix detector, a striped silhouette may be recorded. When the patient moves in the z-direction, each point on the patient is detected a plurality of times in line with the number of detector times. This allows the silhouette to be reconstructed particularly quickly when using a deblurring filter.